Britney Spears Files for Divorce from Kevin Federline

After two years of marriage, 24-year-old Britney Spears is filing for divorce from her rapper husband Kevin Federline.

The pop princess was all smiles and showed no signs of distress Monday night, when she dropped in on David Letterman in NYC. Little did the world know the divorce drama that was about to unfold.

TMZ.com broke the story, revealing that that Spears filed for divorce in Los Angeles Superior Court, and now “Extra's” got the papers.

Brit cites irreconcilable differences and asks for both legal and physical custody of the couple's two children, 1-year-old Sean Preston and 2-month-old Jayden James.

So what was the final straw?

“Extra” has uncovered what may be a clue after spotting Spears in tears with her bodyguard last Thursday in NYC after her husband reportedly stood her up, breaking a dinner date.

This week, they've been apart again, as K-Fed promoted his album in Toronto.

Our Tanika Ray spoke with Federline just last week, when he had nothing but praise for his wife.

“That's my wife, she treats me like a husband,” he said. “That's all that I need.”

But Kevin might need a lot more than that to continue his superstar lifestyle.

TMZ.com reports that the couple has an iron-clad pre-nup, and Spears has hired Laura Wasser, the same high-powered Hollywood lawyer who represented Nick Lachey in his split from Jessica Simpson.